Low excess losses in a Y-branching plastic optical waveguide formed through injection molding

All-POF coupling ratio-imbalanced Sagnac interferometer as a refractive index sensor

A polymer optical Sagnac interferometer is proposed as a compact and low-cost refractive index sensor for the first time to our best knowledge. The Sagnac interferometer is fabricated by only one piece of fiber to facilitate its fabrication and to avoid losses due to misalignment or fusion. The coupler was developed based on chemical and twisting techniques of ∼5cm of fiber. We modified the coupling ratio by varying the refractive index of media surrounding the coupler and consequently modified the transmission. For several values of mass percent concentration of sugar solutions surrounding the coupler, we found that transmittance decreases as the mass concentration increases. However, the decay is faster for the low concentration, while the decay is slower for higher concentrations. Two sets of experiments were carried out, at high (≥ 1 gm/100 ml) and low (<1gm/100ml) mass concentration of sugar solutions. The calibration of the sensor was done at 733 nm, where the response of the interferometer displays larger transmission variations for different solutions. The refractive index estimation was possible by correlation of the transmittance function (calculated by fitting the experimental data) with a linear refractive index model. The estimated resolution of the system is 0.057 weight percent of sugar solution, determined by the noise of the system.

Optical performance of symmetrical and asymmetrical Y-branch couplers for plastic optical fibers

The excess loss and output optical power ratio of symmetrical and asymmetrical Y-branch couplers for plastic optical fibers (POFs) are studied in this work. A ray-tracing model for the Y-branch coupler is derived to investigate the effect of coupling parameters on its optical performance. The coupling parameters, namely coupling angle, axial displacement, and refractive index of filling medium between the emitting-end and receiving-end POFs, are studied. The simulated and measured results indicate that the coupling efficiency is sensitive to all these coupling parameters. A minimum excess loss of approximately 0.83 dB is observed for the symmetrical Y-branch coupler. It is found that both the excess loss and the output power ratio are increased with the increase of the refractive index of the filling medium and the total coupling angle (α+β) for the asymmetrical Y-branch coupler. The experimental results indicate that the maximum output power ratio P1∶P2 is found to be 3.8∶1 for excess loss of less than 2.8 dB for the asymmetrical Y-branch coupler.

Acrylic-Based 1x2 Plastic Optical Fiber Coupler Device Manufacturing Using EGX400 Desktop Engraver System

An all-acrylic-based 1x2 plastic optical fiber (POF) coupler has been designed and manufactured. The optical device is based on a simple 1x2 Y-branch coupler design with a middle high index contrast waveguide taper and splitting ratio of 50:50. Device modeling has been performed using non-sequential ray tracing with an insertion loss of 4.68 dB. Machining of the optical device has been performed using EGX400 desktop engraver system. 1 mm milling tool size with machine spindle speed of 15,000 rpm has been utilized. A simple optimization on the milling process prior to machining improved the coupling surfaces between the POF fibers and the waveguide taper. POF fibers are inserted into the engraved u-grooves and are passively aligned to the waveguide taper. The measured insertion loss is 7.5 dB and with a splitting ratio of 50:50.

Bidirectional optical coupler for plastic optical fibers

We have developed a low-loss bidirectional optical coupler for high-speed optical communication with plastic optical fibers (POFs). The coupler, which is fabricated by an injection molding method that uses poly (methyl methacrylate), has an antisymmetric tapered shape. We show that the coupler has low insertion and branching losses. The tapered shape of the receiving branch reduces beam diameter and increases detection efficiency coupling to a photodetector, whose area is smaller than that of the plastic optical fiber. The possibility of more than 15-m bidirectional transmission with a signaling bit rate up to 500 Mbits/s for simplex step-index POFs is demonstrated.

Fabrication of large-core, high-Δ optical waveguides in polymers

The realization of polymer optical waveguides that have a large core size and high refractive-index difference (LCHD) Δ transmission characteristics is presented. A fabrication procedure for the waveguide based on vertical dip coating and reactive ion etching has been studied. To achieve the lower propagation loss, this procedure includes two original techniques, i.e., the lamination of thick polymer films and sidewall flattening. With these techniques, Δ of 5.4% and a 80 µm × 83 µm core polymer waveguide with 1.4-dB/cm propagation loss were achieved at 680 nm. The LCHD polymer waveguides are useful for practical power-transmission devices.